1. Field of the Invention
The invention relates to a drilling template, a method for attaching a drilling template to a three-dimensionally-shaped workpiece and a method of drilling a workpiece with the template.
2. Discussion of Background Information
The use of drilling templates is always advantageous if axial forces occur in the processing of a workpiece which could cause a faulty positioning of the workpiece. This can occur not only during drilling but also, e.g., during grinding or countersinking.
For example, it is known from the field of aircraft construction, when joining several fuselage sections or when attaching the wings, the empennage and the like to a fuselage section, to rivet or screw the members to one another. To prepare the members for this connection, the members are first drilled through. However, in order to ensure an accurately fitting alignment of the drillings of both members to be connected, the members are first joined together and subsequently jointly drilled through. The precise alignment of the drilling sites in this process is ensured by using drilling templates.
A guiding of the drilling machine can be accomplished by means of so-called jig bushings. Known bushings of this type include those made by Carr Lane Manufacturing Co., St. Louis, Mo., USA (www.carrlane.com). Depending on the embodiment used, the jig bushings can be used as standard bushings to position hand-held drills, or to stop drill feed units, i.e., drilling machines with their own feed mechanism. In particular, in the field of aeronautics, no standard templates are known. This is because the complexity of each individual section requires individually designed or custom made templates. This custom nature of the templates applies to the contour or shape of the templates, as well as to the positions of the individual drill sites.
Such known drilling templates are typically metal plates which are milled from a full material block. In most cases, the metal plates have a slightly curved shape in order to conform to the workpiece surface, which usually also has a curved, and thus three-dimensional shape, i.e., they are usually do not have, e.g., a flat surface running in a single plane.
The drilling templates used in practice, on the one hand have the disadvantage that, while they are highly accurate, they need to be made with a three-dimensional production from a material block. This requires considerable financial and technical expense. As a result, such drilling templates are correspondingly expensive.
These drilling templates also have the disadvantage that, although they are manufactured to design specifications with high precision, in practice, however, differences are encountered between the workpiece surface and the surface of the drilling template, and such differences often cannot be ruled out. A subsequent reworking of the drilling template is often required in order to adapt it optimally to the geometry of the workpiece surface actually present. This results in considerable time delay and produces considerable additional expense.